Mac users who have prided themselves on using one of Apple's older operating systems may want to rethink that decision. Although no official announcement has been made, it's clear Apple will no longer provide support for its Snow Leopard operating system (OS X 10.6), leaving one in five Macs vulnerable to cyberattacks.

Users of the 4-1/2-year-old operating system were also left out in December when Apple patched Safari for its three most recent operating systems but not for OS X 10.6. The last update it received was in September 2013.

The old but popular operating system was still running on 19 percent of Macs at the end of January, more than its predecessor, Lion, which accounted for 16 percent and almost as much as Mountain Lion, ComputerWorld reports. Mavericks users makeup 42 percent of the Mac population.

One of the main reasons users report sticking with Snow Leopard is that there’s simply no reason to change something that already works well. Others are dissatisfied with the direction Apple has taken in terms of its user interface. Snow Leopard is also the last operating system to support PowerPC applications.

But from a security standpoint, upgrading to an operating system that receives regular updates is the smart thing to do. Now that Snow Leopard is no longer being patched, the vulnerabilities hackers find could be used to take over a computer, spy on users and steal sensitive information.

Although Apple is continuing support for Lion and Mountain Lion, those users have the option of upgrading to Mavericks for free.